Purlins Roof Truss

Generally the purlins are so spaced that they are supported over the top chord joints of the truss.

Purlins roof truss.

Adding purlins between heavy timber trusses is an elegant way to reduce the cost of a timber frame roof because purlins permit an increased on center distance between trusses so you purchase fewer trusses. In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof. The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge. In post frame construction roof purlins are the members running the lengthwise direction of the building either placed on top of or between the roof trusses or rafters to attach the roof steel or other roof sheathing to.

The roof truss structure and design is integral to roof structural integrity and shape. An added benefit are the strong lines that purlins create by running parallel to the ridge beam s. Amongst differences are how to space trusses two four eight 12 foot or numerous other possible centers. So i would like some info on purlins.

Purlins are beams of light sections spanning between trusses carrying dead load of roof live load and wind load. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and or the building walls steel beams etc. A common arrangement is a rafter and purlin system which combines purlins and rafters.

In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats. Purlins 24 oc are typical along with the bottom bracing shown. This article and series of illustrated diagrams shows you all the parts of a basic roof truss king truss and queen truss. Purlins transmit these loads to the trusses.

To strengthen the roof system truss clustering cross bracing and wind bracing is recommended at both end of the buildings and every 20 for longer span buildings. There are many types of roof trusses as wall as many types of roofs more types than there are parts. Purlins are dimensional lumber that are fastened to the top chord of trusses connecting them together for bracing purposes. Roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.